This invention pertains to a method for the production of antibodies and, in particular, to a simple and fast method for producing large quantities of IgG antibodies to specific antigens.
Generally, the term "antibody" refers to a protein that appears in the serum and certain cells of a vertebrate in response to the introduction of a protein or some other macromolecule foreign to that vertebrate species. This foreign molecule which stimulates antibody production specific for that molecule is called an "antigen". The specific antibody molecules generated to an antigen can combine with that antigen to form an antigen-antibody complex which destroys or alters the properties of that antigen. The production of antibodies and the binding of the antibodies to antigen molecules is one mechanism used by the body to fight disease-causing agents that have antigenic properties and to neutralize foreign toxic substances. This process is called the humoral immune response.
Antibodies produced in the immune response are divided into five classes that are designated IgG, IgA, IgD, IgE, and IgM. These classes are structurally related and each contains two heavy (H) chains and two light (L) chains, which are connected mainly by disulphide bridges and/or hydrogen bonds. Each class performs a distinct function in the immune response. For example, IgM antibodies are present in larger concentrations in the early stages of an infection, IgG antibodies are long-lasting in serum and promote the phagocytosis of microbes to which they have bound, IgA antibodies are the most abundant antibodies in gut and respiratory secretions, IgE antibodies promote allergic responses and the elimination of helminthic parasites, and IgD antibodies, which are abundant on the cell membranes of lymphocytes but scarce in serum, have a major role in the control of humoral immune responses.
For many antigens the production of antibodies can be initiated simply by injecting the antigens into an immunocompetent vertebrate. Such antigens stimulate the production of antibodies at serum concentrations sufficient to destroy the antigen and retain the "immunity" to that antigen for long periods. These antigens are called "strong antigens". In contrast, some antigens, perhaps because of their size or chemical composition, do not stimulate the production of antibodies when injected by themselves into a vertebrate. The vertebrate cannot, therefore, generate an immune response to such antigens under these circumstances. Immune responses to such "weak antigens" can be generated, however, if they are injected in combination with an adjuvant, such as mineral oil, killed tuberculus bacilli, Al(OH).sub.3, or killed B. pertussis bacilli.
A third class of compounds, the "haptens", fail to generate specific antibody production even when injected into animals along with an adjuvant. Haptens often can, however, generate strong antibody responses if they are physically bound to an antigenic carrier molecule and the hapten-carrier complex is injected into an animal. In general, the more strongly antigenic the carrier to which the hapten is bound, the greater will be the anti-hapten antibody response.
When it is not possible or practical to induce an immune response to an antigen or hapten in an animal by injecting the antigen by itself, with an adjuvant, or bound to an immunogenic carrier, it may still be possible to confer upon that animal the protective effects of the appropriate antibody. This may be acomplished by "passive immunization", a process in which a second animal, often of a different species, is stimulated to produce antibodies to the antigen in question, and serum or purified serum antibodies from the second animal is injected into the first. This process effectively transfers the "immunity" to the recipient animal.
However, neither of these techniques have been effective for some weak antigens and haptens of strategic, commercial, and medical importance such as bacterial capsular polysaccharides, the tricothecene T2, and bacterial lipid A. The stimulated production of antibodies is nonexistant or so low that attempted isolation of the antibody from serum would be impractical because of the large volume of serum needed to obtain a usable quantity of antibody. Similarly, production of the antibody is sometimes so slow that it may take several weeks or months to obtain any useful quantity of the antibody. A method that can induce formation of antibodies which can combat these and other haptens is, therefore, needed.